Synergistic flame-retardant compositions



United States Patent O 3,547,877 SYNERGISTIC FLAME-RETARDANT COMPOSITIONS Christos Savides, Iiscataway Township, Middlesex County, N..l assignor to American Cyanarnid Company, Stamford, Conn, a corporation of Maine No Drawing. Filed July I, 1968, Ser. No. 741,330

Int. Cl. CllSf 45/60; (108g 51/60 U.S. Cl. 26045.8 10 Claims BACKGROUND OF THE INVENTION The production of thermoplastic resin compositions which are flame-retardant is of considerable commercial importance in that such articles as castings, moldings, foamed or laminated articles, etc. are required, or at least desired, to be resistant to fire and flame and to possess the ability to endure heat without deterioration. Typical illustrations of applications of such compositions include castings for live electrical contacts which should not be ignited by flame or sparks, structural members such as pipes, wall coverings, wall paneling, windows, etc. and such items as ash trays, waste baskets, fibers and the like.

The use of certain additives for the purpose of reducing the flammability of various thermoplastic polymers is well known to those skilled in the art. Among the additives currently employed for such a use are various specific types of phosphorus-containing compounds. These phosphorus compounds are generally used either alone or in combination with other materials such as aliphatic or aromatic antimonous compounds. Certain analogous materials such as chlorostyrene copolymers, chlorinated parafiin waxes, alone or with antimony oxide or phosphorus compounds are also known to be effective flameretardants for resinous materials. One drawback of many of these known compounds and combinations of compounds, however, has been the fact that generally large amounts, i.e., upwards of 45%, of the additive must be in corporated into the polymer in order to render it reasonably flame-retardant. Such large quantities of additive ofttimes deleteriously alter the properties of the polymer and moreover, some additives tend to crystallize or oil out of the polymer after a relatively short time of incorporation therein.

Furthermore, these prior art systems generally are thermally unstable and, as such, are not suitable for in corporation into polymeric materials which require high temperature processing conditions because they tend to discolor or otherwise degrade the resultant processed polymer rendering it unfit for ultimate commercial applications. Additionally, most of the prior art additives are liquid in their natural or most common state and therefore may affect other physical properties of the polymeric material to which they are added.

SUMMARY I have now found that superior flame-retarding properties can be imparted to thermoplastic polymers by incorporating into the polymer a synergistic combination or mixture of (A) a compound having the formula:

wherein R and R taken together constitute an oxygen atom or R and R taken separated are, individually, a hydroxy radical, an alkoxy radical of 1-8 carbon atoms, inclusive, or a haloalkoxy radical of 14 carbon atoms, inclusive and (B) a phosphine having the formula:

wherein R R and R individually, represent an aryl radical of 610 carbon atoms, inclusive, an alkyl radical of l-6 carbon atoms, inclusive, or a hydroxy or cyano substituted alkyl radical of 1-6 carbon atoms, inclusive, no more than one alkyl substituent being present in the phosphine if the number of carbon atoms in the alkyl group is less than six.

The novel synergistic combinations provide improved flame-retardance over the additives of the prior art and, additionally, generally provide this superior result at lower concentrations than previously believed to be necessary for most of the known additives. The results shown by the use of the above-mentioned flame-retardant combinations are surprising and unexpected in that the combinations provide a greater degree of flame-retardancy than one would expect from the results shown by the use of the components individually, i.e. they are synergistic.

Additionally, the effectiveness of the combinations is achieved in the absence of any third ingredient, such as antimony compounds or chlorinated hydrocarbons. This synergism, moreover, does not appear to be limited to specific combinations, but is broadly applicable to any combination of a compound represented by Formula I and a compound represented by Formula II.

DESCRIPTION OF THE INVENTION INCLUDING PREFERRED EMBODIMENTS As mentioned above, the first critical component of my novel flame-retardant compositions is a compound represented by Formula I, above. These compounds are well known in the art, as are methods of their production, as represented by US. Pat. Nos. 3,152,172 and 3,196,191 which patents are hereby incorporated herein by reference.

As disclosed in said references, the compounds of Formula I are generally prepared by first preparing the anhydride, where R and R together are oxygen, by the reaction of hexachlorocyclopentadiene and cis-4-cyclohexene-1,2-dicarboxylic anhydride. The free dicarboxylic acid and the esters may then be prepared from the anhydride by conventional means, i.e. reaction with an appropriate alcohol or substituted alcohol, e.g. phenol. Alter- 3 natively, the acid or esters may be prepared by reaction of the hexachlorocyclopentadiene and the diacid or diesters of said cis-4-cyclohexene-1,Z-dicarboxylic anhydride.

The anhydride represented by Formula I is a crystalline solid material having a melting point of about 275 C. The other compounds are also solids of high melting points. The compounds of Formula I may be used in concentrations ranging from about 1.0% to about 20.0%, by weight, based on the weight of the polymer to which they are added.

The second critical component of my novel flameretardant compositions is a phosphine represented by Formula II, above. These phosphines may be produced by any known procedure, one of which is disclosed in US. Pat. No. 2,912,965 which patent is hereby incorporated herein by reference.

The phosphine may be incorporated into the polymeric material in concentrations ranging from about 1.0% to about 20.0%, by weight, based on the weight of the polymer to which it is added.

The term aryl radical, as used herein in regard to the substituents R R and R of Formula II, above, is meant to include not only carbon-hydrogen cyclic compounds but also lower alkyl and halogen ring-substituted phenyl compounds and the scope of the instant invention should be construed so as to include compounds falling within this definition.

The ratio of the compound represented by Formula I to the compound represented by Formula II should range from about 3 to l to 1 to 3, respectively, in the polymer.

Any thermoplastic polymeric material may be rendered flame-retardant by the incorporation therewith of the above-identified flame-retardant combinations. Specifically, however, the vinyl type polymers, wherein a monomeric material is polymerized, by known methods, e.g. by use of free-radical generating catalysts, irradiation, anionic and cationic catalysts, etc. are those preferred. Examples of the vinyl type polymers which may be used to form my novel compositions are the homopolymers and copolymers of acrylamides and N-substituted acrylamides, polyvinyl acetates, butadiene copolymers, e.g. acrylonitrile-butadiene-styrene copolymers, the polymers of acrylonitrile e.g. acrylonitrile-styrene copolymers, polyacrylonitrile etc.

Additionally and even more preferably, one may incorporate the flame-retardant synergistic combinations mentioned above into such polymers as the homopolymers and copolymers of styrene, i.e. polystyrene, a-methyl styrene polymers, styrene-acrylonitrile copolymers, etc. the a-olefin polymers, such as the homopolymers and copolymers, etc. containing, as the major constituent thereof, ethylene, propylene, such as polyethylene, including high density polyethylene, polypropylene and the like and the acrylate and methacrylate homopolymers produced from monomers having the formula:

wherein R is hydrogen or a methyl radical and R is an alkyl radical having from 1 to '6 carbon atoms, inclusive. Examples of monomers represented by Formula III include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-amyl acrylate, t-amyl acrylate, hexyl acrylate and their corresponding alkyl methacrylates, etc. and copolymers thereof with one another and with minor amounts, i.e. not more than about 10%, by weight, of comonomers such as acrylonitrile, styrene, etc.

Also such polymers as the polyamides, e.g. adipic acidhexamethylenediamine reaction products; the polycarbonates, i.e. phosgene-Bisphenol A reaction products; the socalled impact polymers, i.e. rubber-polymer blends such as blends of polystyrene with 510% of butadiene-styrene,

the ABS type resins, e.g. blends of butadiene-styrene and styrene-acrylonitrile; blends of grafted polybutadiene etc. with hard, resinous polymers such as terpolymers of methyl methacrylate, styrene and acrylonitrile etc., and flammable plasticized polymers such as plasticized polyvinylchloride, and the like may be made flame-retardant by the incorporation therein of the synergistic combinations discussed hereinabove.

The novel flame-retardant combinations claimed here in may be added to the various polymers, as such, or as individual components, by any known method. That is to say, the flame-retardant components may be added to the polymer as such, or in combination by (l) milling the polymer and the components on, for example, a tworoll mill, in a Banbury mixer, etc. by (2) molding the components and the polymer simultaneously, by (3) extruding the polymer and components or by (4) merely blending all the materials together in powder or liquid form and thereafter forming the desired ultimate product. Additionally, the flame-retardant components or combination may be added during the production of the polymer, i.e. during the monomer polymerization, provided, however, that the catalyst, etc. other eonditions and other ingredients of the polymerization system are inert thereto.

It is also within the scope of the instant invention to incorporate such ingredients as plasticizers, dyes, pigments, heat and light stabilizers, antioxidants, antistatic agents, photochromic materials and the like into the flatneretarded polymer compositions claimed herein.

The following examples are set forth for purposes of illustration only and are not to be construed as limitations on the present invention except as set forth in the appended claims. All parts and percentages are by weight unless otherwise specified.

METHOD OF TESTING Any appropriate flame-retardance test may be used to determine the flame-retardant properties of any specific combination of compounds represented by Formulae I and II, above. One test I have found to be reasonably eflicient is a modified version of that test identified as ASTM-D63556T. The specifications for this test are: a cylindrical extrudate 68 in length, 0.045 in diameter is prepared using a melt index apparatus (ASTM-D- 1238627), marked at the 1" and 5" lengths and then supported with its longitudinal axis horizontal. A Bunsen burner with a 1'' blue flame is placed under the free end of the strip and is adjusted so that the flame tip is put in contact with the strip end nearest the 5 marking. At the end of 30 seconds, the flame is removed and the specimen is allowed to burn. If the specimen does not continue to burn after the first ignition, it is immediately recontacted with the burner for another 30 seconds. If, after the two burnings, the strip is not burned to the 5" mark, the specimen is designated as nonburning." If the specimen has burned to the 5" mark but not to the 1" mark it is designated as self-extinguishing.

EXAMPLE 1 To parts of polypropylene are added 10 parts of triphenyl phosphine and 5 parts of 2,3-dicarboxy-5,8- endomethylene-5,6,7,8,9,9-hexachloro 1,2,3,4,4a,5,8,8aoctahydronaphthalene anhydride (hereinafter sometimes called DEMON). The resultant mixture is placed in a suitable blender and dry-blended for 4 hours. The blended product is then transferred to a melt-index apparatus whic is preheated to 250 C. Following one minute of aging, a 2.2 kg. weight is placed on the plunger and an extrudate of 68 inches in length is obtained. This specimen is marked and tested according to the above-enumerated flame-retardance test. The results are set forth in Table I, below.

Various other flame-retardant combinations are then incorporated into various other resins according to Example l and comparisons are made between the resultant compositions and control compositions. These results are 3. A flame-retardant comgosition according to claim 1 also set forth in Table 1, below. wherein (Z) is diphenylbutyl phosphine.

TABLE 1 Phosphine Flame- Ex. R2 R3 R4 Percent DEMON derivative Percent Polymer r s i ilts 1 Q 10.0 DEMON 5.0 Polypropylene Passed.

5 .do r 0....

6 cyelohexyl. eyclohexyl.

7 do "do d0 W 8 p-ehlorophenyl.-. p-chlorohpenyl. p-cholorophenyl... 9 do do 19 phenyl cyelohexyl Z-cyznoethyl 20 do d (1 d0 Failed. p ohtl1 10 Polylpropylene. Passed.

0 5 Polydstyrene 0 Methyl diester. 15. 0 Octyl diesten All of the products produced according to Examples 1 4. A flame-retardant composition according to claim 1 to exhibited excellent flame-retardance, as indicated wherein (2) is tris(2-cyanoethyl)phosphine. therein, and, additionally, each and every system ex- 5. A flame-retardant composition according to claim 1 hibited little or no color change when subjected to high wherein R and R together constitute an oxygen atom. temperature processing conditions. 6. A flame-retardant composition comprising a styrene What is claimed is: polymer or a polyolefin having incorporated therein a 1. A flame-retardant composition comprising a comflame-retarding amount of the composition of claim 1 the bination of (1) a compound having the formula: amount of each component of the combination being less than that amount at which the component indi- Y vidually functions similarly to the combination in the C H CH2 0 same polymer. ClO i \IC/ g 7. A flame-retardant composition-according to claim 6 1| 0012 l wherein said thermoplastic polymer is a polyolefin. C1 C\ l 8. A flame-retardant composition according to claim 6 C H CH2 0 wherein said thermoplastic polymer is polypropylene.

I 9. A flame-retardant composition according to claim 6 wherein said thermoplastic polymer is polypropylene and wherein R and R taken together, constitute an oxygen R and R together form an oxygen atom.

atom and IR and R taken individually, constitute a hy- 10. A flame-retardant composition according to claim droxy radical, an alkoxy radical of 1-8 carbon atoms, 6 wherein said thermoplastic polymer is polypropylene, inclusive, or a haloalkyl radical of 14 carbon atoms, R and R together form an oxygen atom and R R and inclusive and (2) a tri-substituted phosphine having the R are phenyl radicals.

formula:

References Cited R UNITED STATES PATENTS 3,152,172 10/1964 Roberts et al. 26O468 3,334,064 8/1967 Bailey 26045.7 Wheltilll R2, R3 and R4 are, ll'ldlVldllally, alkyl ffldlCfllS 3 45 4 2 10/19 7 inh et 1 of 1-6 carbon atoms, inclusive, aryl radicals of 6-10 3442980 5/1969 Grabowski carbon atoms, inclusive, OI hydroxy OI cyano substituted Dunkel et 1 alkyl radicals of 16 carbon atoms, inclusive, no more than one alkyl substitutent being present in the phosphine HOSE A T AYLOR, Primary Examiner if the number of carbon atoms in the alkyl group is less than six the ratio of (1) to (2) ranging from about 3 to HOKE Asslstant Exammer 1 to 1 to 3, respectively. U S C1 X R 2. A flame-retardant composition according to claim 1 wherein (2) is triphenyl phosphine. 252-8.l; 26045.85, 45.9, 45.95

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. j,547,877 Dated December 15, 1970 InventOflS) Christos Savides It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 1, column 5, line 57, "haloalkqyfi should be haloalkoaqy Signed and sealed this 114th day of December 1971.

(SEAL) Attest:

ROBERT GOTTSCHALK EDWARD M.FLE1CHER,JR. Attesting Officer Acting Commissioner of Pa 

